An Indonesian Navy ship sets sail at dawn from the naval base in Banyuwangi, East Java province on April 25, 2021, as the military continues search operations off the coast of Bali for the Navy's KRI Nanggala (402) submarine that went missing April 21 during a training exercise. Photo: Sonny Tumbelaka / AFP

JAKARTA – More than a week after their unannounced arrival, three Chinese salvage vessels remain on the scene of the sunken Indonesian submarine Nanggala 402 with few clues if the stricken vessel can be raised from its final resting place off the north coast of Bali.

China is not known for its expertise in deep-sea marine salvage, but according to a senior Indonesian official who spoke with Asia Times it was the first country to offer its help in what otherwise would be an expensive process usually handled by specialized civilian contractors.

In 2001, for example, the raising of the 18,000-ton nuclear submarine Kursk, carried out by a Dutch-led international consortium, cost the Russian Government US$62 million. Although far bigger than the Nanggala, it was only 160 meters below the surface.

The People’s Liberation Army Navy (PLAN) salvage vessel Yongxing Dao 863, the research ship Tan Suo 2 and the tug boat Nantuo, left their Hainan port soon after the call went out, but inexplicably switched off their transponders as they entered Indonesian waters.

That set off an alarm among segments of the Indonesian Navy who were not aware their mission had been cleared by Chief Maritime Affairs Minister Luhut Panjaitan and Defense Minister Prabowo Subianto, both retired army generals.

Indonesia has become much more alert to Chinese incursions into its Economic Exclusion Zone (EEC) since an incident in 2016 when an armed Chinese Coast Guard cutter seized back a fishing trawler intercepted north of the Natuna islands.

In the past year, Jakarta has also become aware of the increased transit through Indonesian waters of Chinese research vessels, which are suspected of dropping off drones used to map the seabed and other conditions conducive for submarine warfare.

The Yongxing Dao is equipped with a mini-submarine capable of reaching depths of 1,000 meters, along with an underwater robot, side-scan sonar and a multi-beam echo sounder. But navy spokesmen have stressed the difficulty of the task ahead, particularly with the presence of live torpedoes.

The Yongxing Dao in a file photo. Image: Supplied

Strangely, little has been reported about the salvage operation since the Chinese flotilla arrived on May 3-4, 12 days after the German-built Type 209 submarine went missing and only a week after the wreck was found 40 kilometers north of Bali.

The senior Indonesian official said the salvage operation may only be able to recover some but not all of the 1,300-ton submarine, now lying in three parts on the seabed at a depth of nearly 850 meters. He indicated the navy was seeking a second opinion.

Although submarines do not carry black boxes, experts believe it may still be enough to determine the cause of the accident, which killed the 53-man crew during a live-fire exercise at the approaches to the Lombok Strait that separates the islands of Bali and Lombok.

The official appeared to buy into the questionable narrative, widely shared in government circles, that the ill-fated submarine was driven to its doom by a sudden “internal gravity wave,” a phenomenon that causes extreme downward turbulence similar to that experienced in an aircraft.

Not only would it be the first submarine ever sunk in this manner, but analysts say it would tend to absolve the Indonesian Navy of any suggestion the tragedy was caused by human error, such as a misfiring torpedo or an engineering fault.

Even then, sources close to the military say the sinking may have ended Navy Chief of Staff Admiral Yudo Margono’s chances of replacing armed forces (TNI) commander Air Chief Marshal Hadi Tjahjanto when he retires on December 1.

Because it is nominally the navy’s turn in the rotation, Margono has been favored up to now over Army Chief of Staff General Andika Perkasa, son-in-law of politically wired former intelligence chief Abdullah Mahmud Hendropriyono who would only have a year in the job before he reaches retirement age. 

Despite it appearing to receive widespread acceptance among the Indonesian brass, naval analysts are highly skeptical about the “internal wave” theory, arguing that the boat would have had to have lost all power before it could be dragged into the depths.

The Indonesian Cakra class submarine KRI Nanggala 402 (C) setting out from the naval base in Surabaya in an undated file photo. Photo: AFP / Handout / Indonesia Military

Internal waves are generated by strong ocean currents flowing over an undulating ocean floor, a chaotic motion submariners have been aware of since the mid-1960s and are normally well-prepared to deal with in the course of daily operations.

According to Callum Shakespeare, a senior lecturer in climate and fluid physics at the Australian National University, the seas around Indonesia have a perfect combination of these factors: a network of deep basins connected by narrow, shallow channels through which tidal currents flow.

“Without swift action to counteract the wave motion, a submarine could be quickly carried below its maximum operational depth, leading to hull failure and sinking,” he wrote in The Maritime Executive, a maritime industry trade publication.

Other possible causes of the Nanggala disaster may be more difficult to explain, with one analyst noting that one of the few photographs released so far shows what looks like an outward protrusion in the starboard bow section. 

Daniel Craig Reed, a former US Navy submariner who claims to have “inside information” about the tragedy, says there are similarities to the loss of the Kursk and the Argentinian Type-209 submarine ARA San Juan, which went down in the South Atlantic in late 2017.

“Older model diesel-powered submarines are plagued by propulsion system malfunctions, such as battery shorts, fires and explosions,” the author of Red November, Spies of the Deep writes in the American Thinker, an online magazine.

In the San Juan’s case, the cause was seawater leaking through the snorkel into the forward battery compartment, causing a fire which the crew fought for two hours before the rapidly descending boat imploded, killing all 44 aboard.

Describing the lead up to Nanggala’s sinking, Reed notes that the boat reported battery power issues before requesting permission to dive in preparation for the test-firing of two Surface and Underwater Target (SUT) torpedoes.

Indonesian military chief Hadi Tjahjanto (C) speaks during a press conference in Denpasar on April 24, 2021, as search operations continued off the coast of Bali for the Navy’s KRI Nanggala (402) submarine that went missing on April 21. Photo by Yuda Marutha/AFP

“An hour later,” he writes, “the training task force commanding officer authorized the shots and the Nanggala flooded its torpedo tubes. The navy chief of staff said it fired both, an unloaded practice and a live torpedo, before contact was lost.”

Reed says a specialist from the navy’s weapons materials and electronics service was on board to observe the firing of the AEG SUT 264 torpedoes, a 21-inch heavyweight wire-guided ordnance of German design introduced in the late 1960s.

Indonesian officials deny there was any evidence of an explosion, but Reed also refers to the circumstances surrounding the fate of the Kursk in which the Russians say an unstable propellant caused an initial explosion during the test-firing of an outdated Type 65 torpedo.

Intelligence specialists later determined the Kursk was, in fact, test-firing a top-secret Shkvalrocket torpedo, which became lodged in the tube and blew off the aft torpedo tube door. Minutes later a secondary explosion did the rest of the damage.

As for the Nanggala, Reed says: “If a practice torpedo became lodged in the tube, or the weapon experienced a ‘hot run’ where the propellor spun before leaving the tube, or if there was a malfunction with the tube or firing system, this could have resulted in serious flooding that sent the sub to the bottom.”

Regardless of the reason, Reed says, “for those of us in the submarine community, this tragedy ignites a host of nightmares, and our prayers go out to those who are suffering during this time of mourning.”